Study On High-Capacity Organic Field-Effect Transistor Non-Volatile Memory

The rapid development of the information technology industry has led to the ever-increasing demand for mass data storage not only within the emerging sector of printed electronics but also for the wider deployment in the Internet of Things,hence driving considerable research activities contributed to develop high-capacity memory devices.This dissertation focuses on the technological development of high-performance non-volatile organic field-effect transistors(OFETs)memory based on novel,solution-processed organic polymer electrets as well as unconventional,yet highly-effective organic semiconductors for high-capacity charge storage.The first part of this work explores the ability to tune the charge-trapping property within organic semiconductor layers to enable OFETs with desired memory functionality.A judiciously-controlled discontinuous n-type organic semiconductor material N,N'-Ditridecylperylen-e-3,4,9,10-tetracarboxylic diimide(P13)is embedded into the p-type semiconducting pentacene layers to enhance charge storage capacity.Such design leads to the demonstration of excellent non-volatile memory devices with reliable data endurance>3000 times,long retention time>10,000 sec,4-level data storage and high mechanical flexibility(10,000 bending cycles).On the other hand,to investigate the stability of OFET memory,this work provides insight into the operational stability of poly(methyl methacrylate)(PMMA)-based OFET memories at different temperatures.The crystallinity of semiconducting pentacene layers is degraded at both low/high temperatures,obstructing charge injection from electrodes.Furthermore,different operational temperatures also impact the film morphologies of both semiconductor and charge-storage layers,hence altering the charge-storage characteristics.Moreover,flexible heterostructure OFET memory using PMMA as charge storage layer exhibits stable memory performance after 10,000 bending cycles.The second part of the dissertation explores the technology for developing charge-storage layers by engineering wide-bandgap nanocolumn-like organic structures into the charge-storage layer to spatially enhance the charge-trapping capacity.Using this approach,OFET memories with retention time>10,000 sec are demonstrated.Then this work further describes the use of polystyrene(PS)/poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-s-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidyl)imi no]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]](944)polymer electret blend that combines the abilities to trap opposite-polarity charge carriers and its application as charge storage layers in OFET memories.The impact of a series of polymer electret blend ratios on the pentacene growth is studied.An optimized condition leads to the development of 6 distinct memory levels and 10,000-sec retention time.In the final part of this work,to simplify fabrication protocols,a universal approach based on a self-assemble process for simultaneous formation of the semiconductor layer and the charge-storage layer is demonstrated with various organic blends of organic small molecules and polymer electrets.Using this approach,fast,reliable non-volatile OFET memories are demonstrated with highly-stable 3-bit,8-level data storage characteristics.